Smooth-surfaced paper body and method of forming same



Jan. 24, 1967 H. P. JOHNSON ETAL 3,300,159

SMOOTH-SURFACED PAPER BODY AND METHODOF FORMING SAME Filed July.24, 1963MULTIPLE 050165 33:55::

"men Puss m spmnz. wmama CURING FOR M016 TURE STABILIZATION rams LEN 07H ABRAOING aura P POROUS Pt. y 70 51.0 TIER TEXZURB Puma/arms BEFd/PEIMPRE G/VA TIOIV IM PR5 G/VA T/O N 11v .904 Pm/n an TH CUTTING T0 UNIT0075i? SURFACE EURIYI-S'h'l/Y G INVENTORS Hams/5R7" RJOI/MS'QN 6LAM/flames f2 w/urzs hrro, as m United States Patent 3,300,159SMOOTH-SURFACED PAPER BODY AND METHOD OF FORMING SAME Herbert P. Johnsonand Lawrence R. Wilkes, Cedartowu,

Ga, assignors to Textile Paper Products, Inc., Cedartown, Ga., acorporation of Georgia Filed July 24, 1963, Ser. No. 297,459 18 Claims.(Cl. 242-41832) This invention relates in general to thesmooth-surfacing of paper bodies and in particular to the formation ofpaper core structures having exceptionally hard and smooth outersurfaces adapting them uniquely for use as textileyarn carriers, as wellas for advantageous core service in a number of other instances such asin the handlingof foils and films.

The prior art has been concerned for some time with the problem ofproviding a fully satisfactory yarn carrier for supporting packages ofthe relatively elastic synthetic yarns, such as nylon and Dacron, whichimpose heavy compressive stresses on a supporting core by reason of thecumulative compressive force generated from the reaction of such yarnsto the winding tension that is necessarily applied as they are woundinto a package.

Yarns of this sort are commonly packaged by producers on tubularsupporting cores. A representative supporting core might have, a lengthof about /2", an inside diameter of perhaps 3 and a wall thicknesssufiicient to provide adequate strength against the compressivestresses. In addition to adequate strength, the supporting core mustalso present a suitab e outer surface for receiving the yarn uponwinding and releasing it upon withd awal. These structural propertiescould be provided without undue difficulty if it were not for thegoverning importance of cost, which has heretofore forced a greatercompromise with the required structural properties than is desirable.

According to the present invention this limiting cost factor iscircumvented by making it possible to form a fully adequate supportingcore from a simple paper body. A spiral wound paper body, for example,may be constructed readily, and at good cost advantage, to providetheneeded strength against the compressive stresses that must be dealtwith; and the outer surface of this body may then be excellentlyconditioned in accordance with the present invention by impregnating theouter spiral wound ply with sulfur and burnishing it smooth.

It has previously been known that sulfur impregnation produces astrengthening and hardening effect on paper (see, for example, US PatentNo. 1,396,060). Insofar as we are aware, however, the prior art has notappreciated the possibility of developing a sulfur-impregnated papersurface by burnishing, which produces a surfacing effect that isexceptional and surprising. Just why this surfacing effect is obtainedupon burnishi-ng has not been determined with any certainty. It may bethat the impregnated sulfur, having crystalized in and on the treatedouter ply, behaves somewhat like a crystalline Wax or resin in responseto burnishing. In any event, the result is exceptional both as to thedegree of surface smoothness and gloss obtained, and as to the scuff andmoisture resistance at the burnished surface.

These and other features of the present invention are described atfurther length below in relation to the accompanying drawings, in which:

FIG. 1 is a side elevation in quarter section illustrating thestructural form of an embodiment of the core structure of the presentinvention, and

FIG. 2 is a schematic flow diagram indicating the manner in which thecore structure of FIG. 1 is formed.

The representative embodiment of the invention illusrated by thedrawings incorporates a spiral wound con- "ice struction of the basicpaper body because spiral winding offers substantial production and costadvantages, as well as providing good strength readily, and thefollowing detailed description of the invention is accordingly based, asa matter of convenient and significant exemplification, on thisadvantageous embodiment.

Before proceeding, however, it should be noted that the basic paper bodymight alternatively be convolutely wound if desired; that theillustrated tubular form of the basic paper body might be other thancylindrical, such as conical, for example; and that, further, the basicpaper body might have any laminated shape adapted for its intended use,or it might be formed otherwise than by laminating, as by molding, forexample.

Also, while the illustrated embodiment has its entire.

outer surface developed in accordance with the present invention, arestricted surface portion might be developed in essentially the samemanner and to equal advantage for particular purposes, as in providing asmooth tip portion on conical textile yarn cores (see, for example, US.Patents No. 1,896,135 and No. 2,014,040). Additionally, while theillustrated embodiment indicates the exceptional surface smoothness thatmay be developed according to the present invention, it should be notedthat the advantages of the invention may also be realized short of thefullest smoothness possible in instances where it is desirable that thesurface have a somewhat textured character, as will be noted furtherpresently.

Returning to a particular consideration of the illustrated embodiment, acore structure is designated generally by the reference numeral 10 asformed according to the present invention to provide the strength andouter surface condition needed for satisfactory service as a supportingcarrier for producers packages of the synthetic yarns that are elasticenough to impose heavy compressive stresses from their wound packageform. In an actual embodiment of the form illustrated, the outer surfacegloss and smoothness of the core structure is readily apparent, as isthe telltale mark of the outer surface seam that reflects its spiralwound construction.

FIG. 1 illustrates the arrangement of this spiral wound construction ofthe core structure 10 as comprising a predominant plurality of innerspiral wound plies 12 associated with at least one outer covering ply14. The inner plies 12 are employed to build the body of the corestructure 10 with adequate strength, and for this purpose they arepreferably formed from a short-fibered hardwood sheet, such as might beproduced from semichemical stock, that has been highly calendered torender it dense and provide good crush strength in the spiral woundstructure. Typically these inner plies 12 have a thickness of about.023" to .024", and about twelve to fourteen such plies are needed tobuild a core structure 10 like the one illustrated in the drawings. Thespiral windin g of these inner plies 12 is carried out in the usualmanner with the spiral wraps of each ply being defined by a slightlyspaced butt seam (as at 12 in FIG. 1), and with the seams of adjacentplies being staggered as they are superimposed.

The outer covering ply 14 is associated in the same spiral windingoperation (as indicated in FIG. 2), although it is preferably of adifferent and special nature for facilitating the ultimate outer surfaceconditioning. Suitably this outer ply 14 consists of chipboard such asis formed from Waste stock, and is characterized by an open and pourousformation. It will normally be used in a thickness of about .016" to.020", and is provided with deckle edges (by abrading) so that it may bewound with a smooth overlapping spiral seam. A thicker outer ply 14, ormore than one such ply, may be employed to facilitate deeper sulfurimpregnation whenever desired in particular instances.

Following spiral winding (as again illustrated in FIG. 2), the resultingtubular structure is cured to prepare it for further processing. Forthis purpose the tubular structure is initially cut to gross lengths ofperhaps twelve feet or so which. are subjected to oven curing to set thelaminating adhesive and drive off the moisture to a level of about 5%.Upon removal of these lengths from the curing treatment, the tubularstructure tends to regain moisture to some extent, perhaps to a level of7V2 but then becomes stabilized against substantial moisture contentvariation, which has the important effect of subsequently maintaininggood dimensional stability.

After curing, the gross spiral lengths are cut to the unit size of thecore structure it) that is to be formed, and the exposed surface of theouter porous ply 14 is then preferably abraded to a blotter-like texturein prepara tion for sulfur impregnation. The sulfur impregnation mightbe accomplished without such abrading, and even without employing aspecial outer porous ply 14, as by pressure impregnation of the sortdisclosed in the previiously noted U.S. Patent No. 1,396,060, but theimpregnation is substantially facilitated if the outer ply 14 has aporous nature and is abraded to invite impregnation.

Immediately prior to impregnation the individual cores 10 are preheatedto preclude undue sulfur crystallization at the surface of the outer ply14. We have found that preheating to a temperature in the order of 125F. accomplishes this result effectively. The following impregnation isthen carried out by immersion in a molten sulfur bath. The bath isprepared by heating powdered commercial sulfur in an open tank to atemperature that is maintained within the range from about 240 F. to 280F. The ends of the cores 1G are plugged so that the impregnation takesplace only at the surface of outer ply 14, and an immersion time ofapproximately four to six min utes produces satisfactory impregnation ofa porous outer ply 14 that has been abraded as previously noted in thecourse of forming a core 10 of the type illustrated.

Upon removal of the impregnated cores 10 from the molten bath the sulfurpickup hardens at once, and they are ready for the final burnishing stepthat particularly characterizes the present invention. At this stage theouter core surface has a dull and discolored appearance and, if theouter ply 14 has been abraded prior to impregnation, the surface napproduced by abrading is still quite evident although modifiedappreciably in texture by the filling effect of the sulfur impregnation.

The final burnishing step amounts in essence to a frictional working ofthe dull, sulfur-filled, outer surface of the impregnated cores 10. Itis suitably accomplished with one or more fine abrasive belts selectedfor polishing action as the frictional working takes place. During thisfrictional working there is only a slight removal of material from thecore surface-not more than about .005" to .007 in preparing cores iii ofthe illustrated type, and the material that is removed appears in themain to be surface situated sulfur. The transformation of the coresurface upon frictional working, however, is truly remarkable andsurprising, for from the dulled surface condition produced by sulfurimpregnation a smooth and glossy surface appears.

Moreover, this smooth and glossy surface has an unusual hardness againststutfing and the like, as well as an excellent resistance to moisture,which apparently results from the sulfur-filled condition of the paperstructure at and adjacent the burnished surface. That is, the fibrousbody of the impregnated paper apparently has its interstices filled withsulfur that has become crystalline and that dominates the changedcharacter of the impregnated paper to fix or set its fibrous structureagainst disturbance by moisture as well as otherwise to stabilize thestructure and strengthen it materially.

The exceptional physical characteristics that are thus provided by asulfur-impregnated and burnished core structure 10 in accordance withthe present invention af ford particular advantage in dealing with thepreviously mentioned synthetic yarns that exert unusual compressivestresses in package form by reason of their elastic nature. The resultof these compressive stresses is a tendency to deform the windingsurface of the supporting core concavely with respect to its length, fora traversing winding pattern is used in building producers packages ofsuch yarns, and the compressive purchase of the end loops formed as thetraverse reverses is less than that of the regularly disposed wrapsbetween the package ends, so that the generated compressive forcesbecome greater towards the lengthwise center of the package from eachend.

Structural strength to withstand these compressive forces can beprovided to a reasonable degree, and the present invention allows theusual specifications for this purpose to be met readily. However,because the extent to which the compressive forces are generated isaffected materially by the adjustment of winding tension, it can happenthat an inadvertently heavy winding tension will result in a concavedeformation of the winding surface despite the structural strengthspecified to prevent such deformation. But even when this happens, theexceptional smoothness and stability of the winding surface that thepresent invention makes possible still allows with drawal of the yarnwindings therefrom substantially as if the concave deformation had notoccurred.

Such a result is particularly significant with a spiral wound corestructure 10, because the outer ply seam of such a structure terminatesangularly at each core end so as to dispose a sharply pointedconfiguration of the ply thereat which normally has a troublesometendency to come loose as a protruding ear formation on which yarn beingwithdrawn is apt to snag and break; and the structural disturbanceresulting from a concave winding surface deformation promotes such earformation. This cannot happen, however, with a sulfur-impregnated andburnished winding surface formed according to the present invention,because a substantial coalescence of the outer ply seam edges occurs toeliminate any potential for ear formation even though there may stillremain some sign of the spiral seam at the winding surface.

As was noted initially, the present invention also lends itselfeffectively to providing the burnished surface, either entirely orpartially, with a textured character, rather than developing it to thefullest smoothness possible. Such a character is sometimes desirable intextile yarn carriers in order to anchor the beginning yarn wrapsadequately against slippage on the winding surface as the building of ayarn package is started (see, for example, US. patents, No. l,634,492and No. 2,219,836). A surface character of this sort, particularly whenthe outer surface ply has been abraded prior to sufur impregnation, canbe provided readily according to the present invention simply bylimiting the extent or de ree of burnishing so that the degree ofsurface working is sufficiently lessened to yield the desired result.The effect obtained may also be regulated, either alternatively oradditionally, by employing somewhat coarser abrasive belts for thesurface working. In either or both of these ways the satiny surfacefinish that is otherwise possible can be modified to have a definitetextured feel. while essentially retaining the advantageous surfacecondition characterizing the present invention with a difference only indegree of smoothness attained; so that when the term smooth is used inthe appended claims it is to be understood as contemplating theforegoing possibility of texturing the burnished surface as desired, aswell as polishing it glassy smooth.

Finally, it should be noted that the exceptional characteristics suitinga core structure 10 formed according to the present invention for use toparticular advantage as a textile yarn carrier in handling therelatively elastic synthetic yarns likewise render the inventionapplicable generally for providing particularly useful core structuresin a number of other instances. The previously noted use for foils orfilms is a significant example, for foil and film materials exhibit apronounced tendency in roll form to take on at each roll convolution adamaging, or at least degrading, impression of any core surfaceimperfection. The present invention makes it possible to provide asuitable core structure readily that is free of surface imperfectionsand excellently adapted for supporting foil or film rolls, either ofmill size or of smaller widths as slit to customer specifications.

The present invention has been described in detail above for purposes ofillustration only and is not intended to be limited by this descriptionor otherwise except as defined in the appended claims.

We claim:

1. A paper body of substantial thickness characterized by a surfacenormal to said thickness that is impregnated with sulfur and burnishedsmooth.

2. A paper body of substantial thickness impregnated with sulfur at andadjacent a surface thereof normal to said thickness and having saidimpregnated surface burnished smooth.

3. A laminated paper body characterized by an exceptionally hard andsmooth surface portion, said paper body having the exposed layer at saidsurface portion impregnated with sulfur and burnished smooth.

4. A tubular paper body characterized by an exceptionally hard andsmooth outer surface, said paper body being formed of laminated multipleplies and having at least the outer ply thereof impregnated with sulfurand the exposed surface of said impregnated ply burnished smooth.

5. A tubular paper body characterized by an excep tionally hard andsmooth outer surface, said paper body being formed of spiral woundmultiple plies, having at least the outer ply thereof impregnated withsulfur, and having the exposed surface of the impregnated outer plyburnished smooth.

6. A tubular paper body as defined in claim 5 and further characterizedin that at least said outer ply has a relatively porous formation forinviting said sulfur impregnation.

7. A tubular paper body as defined in claim 6 and further characterizedin that the inner spiral wound plies are predominantly of dense andhighly calendered stock for providing said paper body with crushstrength.

8. A core structure for supporting textile yarn packages, said corestructure comprising laminated paper plies super-imposed by winding andadhesively secured, and having at least a portion of the outer plyimpregnated with sulfur and burnished smooth at the exposed surface ofthe impregnated ply portion.

9. A tubular core structure for supporting textile yarn packages of thetype that impose heavy compressive stresses on the supporting core, saidcore structure comprising multiple paper plies laminated by winding, theinner plies being predominantly of dense and highly calendered stock forwithstanding said compressive stresses, at least one outer ply being ofa relatively porous formation and being impregnated with sulfur, and theimpregnated outer ply having the exposed surface thereof burnishedsmooth. v

10. The method of investing a paper body with an exceptionally hard andsmooth surface portion, which method comprises impregnating the paperbody at and adjacent said surface portion with sulfur and then bumishingthe impregnated surface portion smooth.

11. The method of forming a tubular paper body with an exceptionallyhard and smooth outer surface, which method comprises laminatingmultiple paper plies in tubular form, impregnating at least the outerply of the laminated body with sulfur, and then burnishing the exposedsurface of the sulfur-impregnated outer ply.

12. The method defined in claim 11 and further characterized in that atleast the outer ply of said laminated body is provided with a relativelyporous formation for inviting said sulfur impregnation.

13. The method defined in claim 12 and further characterized in that theexposed surface of said outer ply is abraded to a blotter-like textureprior to sulfur impregnation.

14. The method defined in claim 11 and further characterized in thatsaid laminated body is cured upon formation to stabilize the moisturecontent thereof, and is then preheated to facilitate subsequent sulfurimpregnation.

15. The method defined in claim 11 and further characterized in thatsaid sulfur impregnation is carried out by immersion in a molten sulfurbath.

16. The method defined in claim 15 and further characterized in thatsaid molten sulfur bath is maintained at a temperature within the rangefrom about 240 F. to 280 F., and said laminated body is preheated to atemperature in the order of F. prior to immersion in said bath.

17. The method defined in claim 11 and further characterized in thatsaid laminated body is formed with inner plies that are predominantly ofdense and highly calendered paper stock.

18. The method defined in claim 11 and further characterized in thatsaid laminated body is formed by spiral winding.

References Cited by the Examiner UNITED STATES PATENTS 1,396,060 11/1921Richter et al. 242118.32 1,634,492 7/ 1927 Dunlap 242-11832 1,716,215 6/1929 Dunlap. 2,017,611 10/1935 Stogner 242-118.32 2,751,936 6/1956Dunlap et a1. 242118.32 X

FRANK J. COHEN, Primary Examiner.

GEORGE F. MAUTZ, Examiner.

4. A TUBULAR PAPER BODY CHARACTERIZED BY AN EXCEPTIONALLY HARD ANDSMOOTH OUTER SURFACE, SAID PAPER BODY BEING FORMED OF LAMINATED MULTIPLEPLIES AND HAVING AT LEAST THE OUTER PLY THEREOF IMPREGNATED WITH SULFURAND THE EXPOSED SURFACE OF SAID IMPREGNATED PLY BURNISHED SMOOTH.